In the market for mobile devices of recent years typified by mobile phones and the like, foldable mobile devices in which the cases of a display part and the cases of an operation part are connected via hinge parts have become a main stream, and foldable mobile devices which are miniaturized and reduced in thickness are in high demand.
As a result, foldable mobile devices which are miniaturized and reduced in thickness are provided to the market one after another. However, when trying to reduce the thickness of the device, developing an excellent design and mechanical strength is always an issue.
For example, Japanese Patent Laid-Open No. 2005-154864 proposes applying plating treatment that has high uniformity to cases that are made of resin, which are used for low voltage product such as a mobile phone and a notebook type personal computer. In this art, the resin case is caused to adsorb a catalyst, a base metal is precipitated over the resin case in an electroless plating bath, the resin case is dipped into a plating bath obtained by adding an organic acid or organic acid salt such as acetic acid or nickel acetate to a nickel sulfamate bath or a nickel-cobalt sulfamate bath, and nickel is electrolytically precipitated so that the thickness of the plating film of nickel is about 5 μm to 30 μm, whereby rigidity and hardness of the resin plating can be enhanced by using nickel sulfamate for the plating bath.